Have you experimented with the Event() feature?
Objects can have several Event properties that fire when some 'event' occurs. Clients can attach EventHandlers to one or more Events and they get notified when the 'event' occurs.
Combined with the new entityToken and attributes features, it's now possible to store any data a plugin might need, along with references to whatever that data applies to - this already lets you right-click on stuff to detect and open your add-in UI if needs be ( markingMenuDisplaying ) along with pre-populating anything that add-in needs to know about the original geometry it created - so the only bit missing of the puzzle now is hooking something that gives the add-in an opportunity to run when anything it cares about changes...
Personally, I'd love some kind of tokenChanged event which simply feeds me a list of every entity token that's changed, any time any of them do - my add-in can then see if any of those tokens relating to stuff it cares about, and process accordingly.
